HMS Inflexible was a Victorian ironclad battleship carrying her main armament in centrally placed turrets. The ship was constructed in the 1870s for the Royal Navy to oppose the perceived growing threat from the Italian Regia Marina in the Mediterranean.
The Italian Navy had started constructing a pair of battleships, and , equipped with four Armstrong 17.7-inch (450 mm) guns weighing 100 tons each. These were superior to the armament of any ship in the British Mediterranean Squadron, and Inflexible was designed as a counter to them.
Inflexible mounted larger guns than those of any previous British warship and had the thickest armour ever to be fitted to a Royal Navy ship. Controversially, she was designed so that if her un-armoured ends should be seriously damaged in action and become water-logged, the buoyancy of the armoured centre section of the ship would keep her afloat and upright.
The ship was the first major warship to depend in part for the protection of her buoyancy on a horizontal armoured deck below the water-line rather than armoured sides along the waterline.
Design
[[File:HMS Inflexible Diagrams Brasseys 1888.jpg|thumb|left|300px|{ { center|Plans of Inflexible as shown in Brasseys Naval Annual}}]] A heavily armoured citadel wide and long was located amidships, which would keep the ship afloat and stable regardless of what happened to the ends. This citadel contained the main guns, the boilers and the engines. The ends were unarmoured, but with a armoured deck 6–8 ft below the waterline to limit damage to the underwater section to keep them buoyant. Coal bunkers were located over the armoured deck and surrounded by compartments filled with cork. The ship had bunker capacity for 400 tons of coal below the deck for use during combat, when the above-deck bunkers would be inaccessible and possibly flooded. The structure above the armoured deck also contained a large number of watertight compartments to further preserve buoyancy. There was also light superstructure to provide crew accommodation, and freeboard in rough weather, although anticipated to be seriously damaged in any major engagement.
Barnaby wanted a ship both broader than existing designs to minimise rolling and as short as possible to reduce its size as a target. Making a ship broader compared to its length was known to reduce its speed, so the innovative technique of water tank tests on models, pioneered by William Froude, was used to finalise a design. This was ten feet wider than Duillo and twenty-one feet shorter, the smallest ever ratio of length to breadth in a metal first class warship.
Once the outline design was agreed, the detailed architectural design was done by William White and she was laid down at Portsmouth Dockyard on 24 February 1874.
Controversy Inflexible was launched 27 April 1876. Later that year the MP Edward Reed, formerly Director of Naval Construction, visited the Italian ships and subsequently questioned their stability if the unarmoured ends were flooded. As Inflexible was of similar design, he raised grave concerns about this to the Admiralty. When this had no effect he publicised his charges in The Times in June 1877. An editorial in the same edition, 18 June, said "it is said that the unarmoured ends are, in fact, the corks on which she floats, that she cannot swim without them, and it would appear that if she lost one she would capsize".
Further exchanges followed until in July, construction was halted on Inflexible (and two other smaller ships, and ) whilst a hastily convened committee examined the design. In their report published in December 1877, they concluded that it would be hard for gunfire to completely flood the unarmoured but heavily compartmentalised and partially cork-filled ends. However, if this was managed then the ship would just be stable, capsizing at about 35 degrees heel.
Work restarted on the ship in December 1877, and the ship was commissioned 5 July 1881, under Captain John Fisher, although she was not completed until 18 October. Her eventual cost was £812,000.